Recently, a variety of types of display devices are actively researched and developed. Among these, much attention is focused on organic electroluminescent (EL) devices. This is because organic EL devices are promising display devices capable of emitting light of high luminance under low applied voltage. An important characteristic of organic EL devices is life (durability), and as such, studies have been made toward further prolonging the life of organic EL devices. As a means to prolong life, luminescent devices of a type comprising a hole-injection layer containing CuPc (copper phthalocyanine) are known (as described, for example, in JP-A-57-51781 (“JP-A” means unexamined published Japanese patent application) and Applied Physics Letters, 15, 69, 1996). However, such luminescent devices are still low in quantum efficiency. Accordingly, there is a demand for further improved devices.
On the other hand, for the development of organic EL devices in recent years, various studies have aimed at improving the external quantum efficiency of the devices. In particular, observation is focused on luminescent devices containing a phosphorescent material, such as tris-phenylpyridine iridium complexes (see WO 00/070655) and tetradentate platinum complexes (for example, octaethylporphyrin platinum complexes) (see U.S. Pat. No. 6,303,238 B1 and U.S. Pat. No. 6,653,564 B1), because high-external quantum efficiency is attained with these devices. However, these phosphorescent materials and devices containing the phosphorescent material have needed life prolongation. In addition, conventional tetradentate platinum complexes (see U.S. Pat. No. 6,303,238 B1 and U.S. Pat. No. 6,653,564 B1) have the problem that light emission is restricted to the color ranging from orange to red, and therefore it is difficult to obtain light emission in the short wavelength ranging from blue to green that is necessary for use in full color displays and multicolor displays.